1. Field of the Invention
This invention relates to field-of-view controlling arrangements, such as privacy screens, made up of microprism or lenticular sheets.
More particularly, the invention relates to a field-of-view controlling arrangement made up of a microprism or lenticular sheet having a plurality of sets of parallel surfaces that intersect to form prisms or lenticular structures, and in which field-of-view control or privacy screening is achieved by:
for sheets made up of parallel xe2x80x9cone-dimensionalxe2x80x9d microprism or lenticular structures having at least two intersecting sets of mutually parallel surfaces, altering a first set of mutually parallel surfaces and at least one second set of the mutually parallel surfaces of the microprism or lenticular structures, and/or portions of the at least two sets of mutually parallel surfaces, by applying a light-attenuating treatment to the surfaces,
for sheets made up of xe2x80x9ctwo-dimensionalxe2x80x9d or polyhedral lenticular structures having at least three intersecting sets of mutually parallel surfaces, or at least one set of curved surfaces extending in directions transverse to directions in which the field-of-view is to be limited, altering at least one set of the mutually parallel or curved surfaces by applying a light-attenuating treatment to the at least one set of mutually parallel or curved surfaces, and
for any type of microprism or lenticular sheet, including a diffusing agent in at least a portion of the sheet, and arranging the surfaces of the microprism or lenticular sheet so that light transmitted along selected optical paths is attenuated before exiting the sheet through a first set of surfaces while light transmitted along other optical paths is relatively unattenuated before exiting the sheet through a second set of surfaces oriented at a nonzero angle relative to each of the surfaces in the first set of surfaces,
thereby achieving a privacy screen that restricts viewing of an image from more than one side of the potential field-of-view.
The privacy screens of the invention represent an improvement over the privacy screens disclosed in copending U.S. patent application Ser. Nos. 09/583,731, filed Mar. 30, 2000, and 09/481,942, filed Jan. 13, 2000, (both incorporated herein by reference), which disclose privacy screens in which privacy screening is achieved by altering just one set of mutually parallel surfaces or facets of a conventional microprism sheet of the type having a single set of xe2x80x9cone-dimensionalxe2x80x9d prisms, i.e., prisms formed by parallel grooves in the sheet, to attenuate light so as to restrict the field-of-view, for images transmitted by the sheet, to only one side of the field-of-view.
The privacy screens of the invention may be used as overlays for video displays, for example to restrict eavesdropping with respect to a computer display, or as window coverings. When used as window coverings, the privacy screens of the invention have the additional advantage that the prisms or lenticular structures that make up the screen may be used to bend incoming light and improve the view from the window. In addition, the privacy screens of the invention may, at desired angles, include embedded images or graphics, and may provide other screening functions such as attenuation of ultra-violet light or other radiation, polarization, and so forth.
2. Description of Related Art
As illustrated in FIG. 1, the privacy screen disclosed in copending U.S. patent application Ser. No. 09/481,942 is made up of a microprism sheet 1 having multiple sets of parallel surfaces 3, 4 that intersect to form prisms defined by adjacent parallel grooves 2.
In order to provide a privacy screening effect, one set of the parallel surfaces 3 is altered by surface treatment to attenuate or scatter transmitted light in selected directions. The result of this arrangement is a simple and inexpensive privacy screen that permits viewing of an image by an observer 25 through the untreated set of surfaces 4, and that prevents viewing of the image through the treated sets of surfaces 3, the angles xcex1 and xcex2 of the respective surfaces determining the range of angles in which viewing is restricted. Uses for the privacy screen described in copending application Ser. No. 09/481,942 include computer monitor overlays that prevent eavesdropping, stereoscopic viewing devices, and two-player video game arrangements such as the one illustrated in FIG. 3, in which an overlay 12 consisting of multiple sheets 6 and 7 is used to restrict viewing by the respective game players of opposite portions of an image displayed on screen 13.
Although the privacy screen described in U.S. patent application Ser. No. 09/481,942 is ideally suited to applications such as the one illustrated in FIG. 3, in which only one side of the field-of-view of an image needs to be restricted, applications such as eavesdropping prevention often call for restriction of viewing from at least two sides. Furthermore, it would be desirable if additional optical effects could be achieved with a single sheet, even if viewing from only one side need be restricted.
One solution to the problem of limiting viewing from more than one side of the field-of-view is proposed in the above-cited U.S. patent application Ser. No. 09/583,731. According to this solution, privacy screens identical to those described in U.S. patent application Ser. No. 09/481,942 are stacked with the treated sets of surfaces oriented in different directions to restrict the field-of-view of an image from multiple sides. While this solution is simple and effective, the present invention proposes two even simpler solutions, both involving use of a single rather than multiple microprism or lenticular sheets.
The two alternative solutions respectively involve use of surface treatment and bulk diffusion materials, and are discussed separately below.
The first alternative solution to the problem of restricting the field-of-view of an image from multiple sides is to use surface treatments similar to those described in the above-discussed U.S. patent application Ser. Nos. 09/481,942 and 09/583,731. However, instead of altering a single set of parallel surfaces or facets of a the microprism sheet to attenuate light so as to narrow the field-of-view of images passing through the sheet, the present invention proposes to achieve privacy screening by altering at least two of the sets of mutually parallel surfaces, portions of the at least two sets of mutually parallel surfaces, or a corresponding set of identically oriented curved surfaces, and in particular by applying a light attenuating surface treatment to the sets of mutually parallel or curved surfaces. The result of such treatment of multiple sets of surfaces is a privacy screen that restricts viewing of an image from more than one side of the potential field-of-view without the need to stack multiple sheets.
As discussed in detail in U.S. patent application Ser. No. 09/481,942, it is of course well-known in general to selectively treat surfaces of a microprism or lenticular structure for the purpose of selectively attenuating light passing through the sheet. However, such treatments had always been, prior to development of the privacy screen disclosed in U.S. patent application Ser. No. 09/481,942, used in a way that attenuates or scatters background light, rather than the image itself, so as to reduce glare or increase image visibility, contrast, or relative brightness. Furthermore, the prior microprism or lenticular structures had always been combined with other structures to form a rear or front projection screen, rather than being used as a stand-alone sheet or overlay used solely for the purpose of privacy screening.
The numerous prior patents disclosing treatment of microprism or lenticular surfaces to attenuate or re-direct background light for purposes of glare reduction, brightness and contrast optimization, or the like, thus tend to teach away from the invention, which involves intentional attenuation of the image itself, in certain directions. Nevertheless, it should be noted that the same surface treatments disclosed in the prior patents may also be used in connection with the present invention, albeit on different surfaces of the sheets. Potentially useful surface treatment techniques include various coating processes such as printing, vapor deposition, or sputtering of opaque or light-scattering materials, delustering, chemical or laser etching, casting, and differential polishing of previously roughened surfaces.
Many of these techniques are disclosed in the following patents directed to microprism sheets in general:
U.S. Pat. Nos. 5,836,096 (Brauer), 5,512,219 (Rowland et al.) 5,446,594 (Nelson et al.), 5,363,237 (Wakatake), 5,316,359 (Lansinger), 5,208,620 (Mitsutake et al.), 4,708,435 (Yata et al.), 4,309,074 (Granieri), 4,309,073 (Nishimura et al.), 4,206,969 (Cobb et al.), 3,971,051 (Baker et al.), 3,902,787 (Sherlock), and 3,718,078 (Plummer),
as well as in the following patents directed to glare reduction screens having a single treated surface arranged generally parallel to the direction of image transmission, thereby effects of background light:
U.S. Pat. Nos. 4,911,529 (Van De Ven), 4,756,603 (Ohtani), 4,165,920 (Brown), 2,909,770 (Pugsley),
in the following patents that disclose use of lenticular or microprism sheets as isotropic light diffusers in rear projection systems:
U.S. Pat. Nos. 4,730,897 (McKechnie et al.), 5,400,114 (Yoshida et al.), 5,457,572 (Ishii et al.), 5,581,407 (Mitani et al.), 5,760,955 (Goldenberg et al.), 6,002,829 (Winston et al.), 6,157,491 (Watanabe et al.), 6,025,897 (Weber et al.), and 6,169,633 (Watanabe), and
in the following patents directed to use of microprism or lenticular sheets to increase the field of view in nonprojection or direct sight type LCD systems:
U.S. Pat. Nos. 5,745,199 and 5,555,476, both to Suzuki et al.
These and other patents offer guidance on altering the properties of optical surfaces, though not for the purposes of the present invention.
This alternative solution to the problem of achieving privacy screening from more than one side using a single microprism or lenticular sheet involves including a diffusing agent in at least a portion or section of the sheet, and arranging surfaces of the microprism or lenticular sheet so that light along selected optical paths is attenuated before reaching the surfaces.
The use of diffusing materials for what may be thought of as xe2x80x9ccollimationxe2x80x9d should not be confused with the use of diffusing materials for collimation in arrangements such as the one disclosed in U.S. Pat. No. 5,837,346 (Langille et al.). In the arrangement disclosed in U.S. Pat. No. 5,837,346, a combination of bulk diffusion and surface texturing is used to achieve the same effect as a Fresnel lens, i.e., causing light incident on the rear of the screen at a wide range of angles to exit the front of the screen in parallel. Although one effect of the present invention is also to achieve xe2x80x9ccollimationxe2x80x9d (in the broadest sense of the word) of the transmitted image, the xe2x80x9ccollimationxe2x80x9d provided by the multiple zone privacy screen of the invention, i.e., attenuation rather than focusing of light incident at non-parallel angles, is not to be confused with the type of collimation conventionally provided in rear projection screens. Whereas the present invention seeks to narrow the field-of-view of an image and prevent the image, or portions of an image, from being viewed at angles outside a desired range, collimators of the type used in rear projection screens seek to concentrate the light without attenuation. This may be accomplished solely by using Fresnel lens structures, with no need for any sort of diffuser, but it can also be achieved, at least according to U.S. Pat. No. 5,837,346, by combining bulk diffusion with surface texturing to impart asymmetrical diffusion characteristics to the screen.
Thus, while the present invention shares with the projection screen described in U.S. Pat. No. 5,837,346, an embodiment that also happens to use bulk diffusion, the functions of the respective diffusion materials differ substantially. The prior collimating diffusion structure seeks to provide a collimating lens effect in which light incident at a wide range of angles exits the screen at a narrower range of angles, while the diffusion structure of the present invention simply seeks to attenuate all light incident on the screen that is outside the narrower range of angles.
One reason for the substantial difference in function between xe2x80x9ccollimatingxe2x80x9d structures of the type disclosed U.S. Pat. No. 5,837,346 and that of the present invention, is essentially that rear projection collimation of the type disclosed in U.S. Pat. No. 5,837,346 requires that the bulk diffusion material have asymmetric or anisotropic diffusion characteristics, whereas the corresponding bulk diffusion materials of the present invention may diffuse light isotropically (although anisotropic diffusion may also work), the privacy screening effect being achieved not by differences in scattering patterns, but in the lengths of the paths through which light traverses the material, resulting in an especially simple privacy screen construction that nevertheless achieves privacy screening on at least two sides of an image.
It is accordingly a first objective of the invention to provide a more versatile field-of-view controlling arrangement in which the field-of-view may be controlled or restricted from any side over any range of angles, including from multiple sides.
It is a second objective of the invention to provide a field-of-view controlling arrangement that can be used not only to restrict the field-of-view from one or more sides, but also to improve or modify images visible in the unrestricted portion of the field-of-view.
It is a third objective of the invention to provide an improved privacy screen that restricts the field-of-view of an image from at least two sides, and yet that consists of a single microprism or lenticular sheet.
It is a fourth objective of the invention to extend the range of applications for the microprism or lenticular privacy screens disclosed in U.S. patent application Ser. Nos. 09/481,942 and 09/583,732 to applications that require multiple privacy zones, without significantly increasing cost or difficulty of manufacture.
It is a fifth objective of the invention to provide a privacy screen that is suitable for use with lenticular as well as microprism sheets, the lenticular sheets offering additional possibilities of image modification or enhancement, including image magnification, while still providing privacy screening effects using a single sheet.
It is a sixth objective of the invention to provide privacy screens having increased versatility and yet that are simple to manufacture and that can easily be adapted for use in a variety of contexts.
It is a seventh objective of the invention to provide privacy screens suitable for use as a computer monitor or television overlay, and which limits viewing of a displayed image to persons situated at a specific range of angles relative to the monitor or television.
It is a eighth objective of the invention to provide privacy screens that may be applied to a window, and which not only serve as a blind, but also can be arranged to improve the view through the window, and/or to replace an undesired view with images or graphics.
These objectives are achieved by:
in accordance with the principles of a first preferred embodiment of the invention, altering at least two sets of mutually parallel surfaces of a microprism or lenticular sheet and a second set of mutually parallel surfaces of a microprism or lenticular sheet that are oriented at different angles relative to a principal plane of the sheet, and/or portions of the two sets of mutually parallel surfaces, so as to attenuate light on selected sides of the field-of-of view for an image transmitted through the sheet by applying a light attenuating surface treatment to the surfaces, or
also in accordance with the principles of the first preferred embodiment of the invention, altering at least one set of mutually parallel surfaces, or corresponding curved surfaces, of a microprism or lenticular sheet in which the microprisms or lenticular elements are formed by polyhedra or other discrete structures such as frustoconical lenticules, and
alternatively, in accordance with the principles of a second preferred embodiment of the invention, including a diffusing agent in the material of the sheet, and arranging selected surfaces of the microprism or lenticular sheet so that light along selected optical paths is attenuated before exiting the selected surfaces.
Each of the two preferred embodiments of the invention provides a privacy screen that can be adapted to restrict viewing of an image from at least one or two sides of the potential field-of-view, with some implementations offering the possibility of restricting viewing from three sides, and of achieving additional optical effects such as expansion of the field-of-view in the unrestricted directions. Furthermore, the privacy screen of each of the two preferred embodiments of the invention is made of a single sheet, which can be arranged to serve as a very simple screen overlay to prevent observers situated on different sides of the screen from eavesdropping.
In one implementation of the first preferred embodiment-of the invention, the above-described surface treatment principles may be applied to a conventional microprism sheet of the type described in U.S. patent application Ser. No. 09/481,942, i.e., a microprism sheet having a plurality of v-shaped grooves forming two sets of parallel surfaces that intersect to form grooves, by surface treating both surfaces of alternate ones of the grooves.
In other implementations of the first preferred embodiment of the invention, the microprism sheets may include truncated prism structures formed by spacing apart the v-shaped grooves, lenticular sheets having v-shaped grooves and one or two-dimensional lens structures, and sheets with grooves on opposite sides of the sheet, either aligned or alternating, and either spaced-apart (to form truncated prism structures) or adjacent (to form v-shaped prism structures).
In still further implementations of the first preferred embodiment of the invention, the sheets to which the surface treatments are applied are polyhedral structures, which may include truncated tetrahedral lenticular structures, tetrahedral structures, other multifaceted or polyhedral lenticular structures, and frugtoconical or similar structures, and in which light-attenuating surface treatments are applied to at least one of the mutually parallel or curved sets of surfaces that form the discrete lenticular structures.
The surface treatments applied may consist of any surface treatments that have the effect of absorbing or scattering light and that can be applied to selected surfaces by means of a mask, control of the surface treatment tool, or use of an appropriate die, including application of opaque or light diffusing coatings, delustering, chemical or laser etching, casting, and differential polishing of previously roughened surfaces, as well as any other surface treatment methods described in the above-cited patents or patent applications, or that are known or may become known to those skilled in the art. Further, as in the privacy screens of the above-cited applications, it is also possible, in addition to surface treatments that merely block or scatter light, to add surface treatments result in the appearance of images or graphics at selected angles.
With respect to the second preferred embodiment of the invention, rather than forming a privacy screen by preventing viewing of an image in the direction of treated surfaces and permitting viewing of the image through the untreated surface (or vice versa), the same effect can be achieved by forming the microprism or lenticular sheet using a bulk diffuser in at least a portion or section of the sheet, the bulk diffuser being preferably concentrated (if not evenly distributed) in the portion or section of the sheet adjacent the light entrance side. In contrast to projection screen diffusers, which seek to collimate light by causing it to bend towards a preferred diffusion axis, the diffuser of the invention should be arranged so that the diffusion effect depends solely on the amount of diffusing material that must be traversed by a particular ray of the image transmitted by the sheet. Although the material of the bulk diffuser may be isotropic, it will be appreciated that anisotropic materials may also be utilized so long as the anisotropy causes greater attenuation in the direction of desired privacy than in the viewing direction,
In the embodiment in which the sheet is made up of parallel v-shaped grooves, the dimensions of the grooves and sheet may generally be the same as those described in copending U.S. patent application Ser. No. 09/481,581, although the invention is not limited to particular groove dimensions. As explained in the parent application, grooves having a pitch on the order 0.12 to 0.14 inches are undiscernable by a person having normal vision at a typical distance from a screen, and thus may be appropriate for the privacy screening structure of the invention. Depending on the shapes of the prisms and the locations of the coatings, it may also be necessary to reduce the pitch and size of the grooves in order to prevent the viewer from perceiving Moirxc3xa9 effects resulting from the contrast between the treated and untreated portions of the sheet.
Also as in the aforementioned patent applications, and especially U.S. patent application Ser. No. 09/583,731, the configuration of the microprism or lenticular sheet may itself be varied by, for example, varying the pitch, shapes, or sizes of the grooves, prisms, or lenses, or the thickness of the sheet, relative to the center or edges of the sheet, or by constructing the sheet as a curved rather than planar structure.
Finally, while the privacy screens of the preferred embodiments of the invention are especially suitable for use in restricting eavesdropping by persons situated above or below a computer monitor or television screen, the invention is not to be limited to a particular application. Instead, it is anticipated that the privacy screen of the invention may be used in any of a variety of potential applications that might involve restricted viewing of an image or scene, including applications in which the privacy screens of the invention are applied to windows to serve as blinds, and applications that involve restricting viewing of more than two sides of the image, for example by surface treating multiple sets of surfaces of a two-dimensional lenticular sheet, or by appropriate use of a bulk diffuser in such a sheet. When applied to a window, the privacy screens of the invention not only can provide privacy and restrict incoming light, but also can modify the view through the window by using the prisms or lenticular structures of the overlay to bend light is selected directions, or modify the view by adding images or graphics visible at selected angles.